1. Field of the Invention
This invention relates to a method of identifying touch points on a touch panel and, in particular, to a method of identifying a palm area for a touch panel and a method for updating the identified palm area.
2. Description of Related Art
Touch panels are very popular input devices applied in an electronic product area or a computer product area. The touch panel can substitute for buttons or keyboards, so electronic products or computer products equipped with the touch panel can be fabricated in a more compact size. The touch panel also provides a hand-writing function allowing a user to directly operate the electronic products.
Touch panels are categorized into many types such as a single touch type or a multi-touch type, wherein the multi-touch type is more popular. The multi-touch panel can only recognize the presence of multiple fingers to determine which function should be performed, such as the screen scaling function and the drag-and-drop function. When the foregoing recognizing method is applied to the small-size touch panel such as the panel of a smart phone, using the fingers to operate the touch panel may not cause any inconvenience. However, as the large-size touch panel comes to the market, the multi-finger based reorganization method may not meet the user's habits. For example, when the user views electronic-books or news via the touch panel, the user may unintentionally put the entire palm on the touch panel. The contact of the palm with the touch panel will cause an error. To improve the identifying methods, U.S. Pat. Publication No. 2011/0012855 discloses a multi-touch device and method for palm rejection. Normally, when a user puts fingers and a palm on a multi-touch panel, the palm will be regarded as a valid touching point. The U.S. patent publication discloses a method for rejecting the touched palm area as shown in FIGS. 14A to 14D, wherein the method comprises:
continuously receiving images including touching points from a touch panel 10;
searching at least one first touching area such as a palm area 40 from the images before fingers 52 or a stylus touching the touch panel 10;
defining at least an untouched area by the at least one first touching area; and
recognizing a touch point being out of the palm area 40 as a reference point, wherein the touch point corresponds to a finger touch or a stylus touch as a reference point 31.
For rejecting the palm area 40, the user must touch the touch panel by a palm 51 at first as shown in FIG. 14A to correctly define the palm area 40. With reference to FIGS. 14B and 14C, after the palm area 40 is defined as an ineffective area, the user can operate the touch panel by the fingers 52 or the stylus. Thus positions of the touching reference points 31 can be correctly identified as shown in FIG. 14D. In the foregoing approaches, the user is required to set the palm area 40 in advance. Therefore, the approach indirectly limits the user's operating habits and is not practical enough.